we will assume that a 0-10Vdc input will be used to measure 4-20ma signal.
Ohms law states: R=V/I where V is the Voltage, I is the current and R is the resistance
R=10V/.020A = 500 Ohms
When 20ma flows through a 500 Ohm resistor, it will drop 10 volts
When 4ma flows through a 500 Ohm resistor, it will drop 2 volts
Therefore, 4-20ma signal through a 500 ohm resister will drop 2 to 10 volts
if you’re using instrument with 4-20mA and connect it to:
1. range 0-20mA – your value of the instrument will be from that 5529 to 27648, value from 0 to cca 5500 will be not showed, but it depends on instrument.
2. range 4-20mA – your value of instrument will be from 0 to 27648.
Fig. 01: Connection of a sensor to a voltage source as a 2-conductor connection
Fig. 02: Connection of a sensor to a voltage source as a 3-conductor connection
Fig. 03: Connection of a sensor to a voltage source as a 4-conductor connection
Fig. 04: Connection of a measuring transducer with voltage output to a current source as a 4-conductor connection
Fig. 02: Connection of a three-wire sensor
Fig. 03: Current measurement with a two-wire sensor